294 NATURE'S TEACHINGS. 



Some years ago, while looking at the account given by 

 Mr. J. Price of a lock invented by Mr. Cotterill, I saw at once 

 that the inventor, whether consciously or not, had followed the 

 mechanism of the eye, as far as metal could be expected to 

 imitate animal fibre. 



In the very centre of the lock there is a small circular 

 opening, resembling the pupil of the eye, and serving to admit 

 the key, just as the pupil admits light. Around this pupil, if 

 we may so call it, are ranged some twenty thin steel slides 

 which move in channels, up and down which they slide. 

 Round the circumference of the lock are a corresponding 

 number of spiral springs, each of which presses on the base of 

 a slide, and forces it towards the centre. 



The reader will now see that the radiating slides of the lock 

 represent the radiating fibres of the iris, and that the spiral 

 springs represent the circular fibres. Both perform the same 

 office, the steel slides regulating the size of the aperture, and 

 the spiral springs pressing them all towards the centre. The 

 key of the lock answers the same purpose as does light in the 

 eye, which by its mysterious pressure enlarges or contracts the 

 pupil. 



This is not the place to describe this very ingenious lock in 

 detail, but I may state that it has never been picked. Even 

 Mr. Hobbs, who tried it for twenty-four hours, gave it up, and, 

 when he saw the interior mechanism, said that if he had tried 

 for a month he should have made no progress. This is an 

 unconscious testimony to the wisdom of following Nature in Art. 



THE MAGIC LANTERN. 



WE are all familiar with the Magic Lantern, whether it may 

 take the form of the mere child's toy, be developed into Dis- 

 solving Views, or throw black shadows on a curtain, in which 

 case it is called by the name of Chinese Shadows. In all these 

 cases the principle is the same. First we have a light behind 

 the object whose reflection is to be seen. Next we have the 

 object itself, and lastly the surface upon which it is reflected. 

 As to the variety of mirrors, lamps, and lenses which are used 

 to produce different effects, we may put them aside as foreign to 

 our present purpose. 



